Blood coagulates by the action of its various components in blood when it contacts foreign matter. Hence, there is need for a high anticoagulant property in materials used for the components of medical articles or instruments, such as artificial hearts, artificial cardiac valves, artificial blood vessel, blood vessel catheters, cannulas, pump-oxygenators, blood vessel by-pass tubes, intraaortic balloon pumping, transfusion instruments and extracorporeal circulation circuits, on the portions that contact blood.
Heparin has been commonly used to provide these medical devices anticoagulant properties, but systemic use of heparin may undesirably lead to the formation of a large number of bleeding sites. Methods have been developed to minimize side effects associated with the use of heparin with limited success (see, for example, U.S. Pat. Nos. 5,270,064 and 6,630,580). Meanwhile, problems associated with systemic drug administration have led to the development of methods for local delivery of the drug. Administering a pharmacologically active drug directly to a patient may lead to undesirable consequences because many therapeutic substances have undesirable properties that present pharmacological, or pharmacokinetic barriers in clinical drug application.
Thus, it is desirable to provide for the deliver of heparin locally from an implantable medical device. In addition, it is desirable to deliver other drugs from such an implantable medical device. Therefore, in the art of drug-delivery implantable medical devices, there is a need for an implantable medical device that has heparin at the surface, and that is also capable of delivering a drug that is not heparin.